Vibratory drilling



Jan. 9, 1962 ECKEL T I 3,016,098

VIBRATORY DRILLING Filed March 11, 1958 2 Sheets-Sheet l JOHN E. ECKELEVERETT H. LOQK INVENTORS BYw (27W ATTORNEY 1952 J. E. ECKEL ETAL3,016,098

' VIBRATORY DRILLING Filed March 11, 1958 2 Sheets-Sheet 2 JOHN E. ECKELEVERETT H. LOCK INVENTORS nv w. ATTORNEY United States Patent 3,016,098VIBRATORY DRILLING John E. Eckel and Everett H. Lock, Tulsa, Okla., as-

signors, by mesne assignments, to Jersey Production Research CompanyFiled Mar. 11, 1958, Ser. No. 720,767

7 Claims. (Cl. 17556) The present invention is concerned with animproved apparatus for drilling well boreholes into the earthssubstrata. The invention more specifically relates to an improvedapparatus for rotary drilling employing a vibratory vertical thrust. Inaccordance with the specific adaptation of the present invention,theenergy dissipation to the surrounding drilling liquid when employinga vibratory bit assembly, particularly a high-frequency bit assembly, ismaterially decreased by the utilization of a unique gaseous buffer zone.

In the exploration for oil, the art of drilling well boreholes intosubterranean areas of the earth has been widely investigated andextensively developed. The techniques employed are many, and a widevariety of drilling bits and associated apparatu have also beendeveloped. One conventional procedure is to, attach a suitable bit onthe end of a pipe string and to rotate the bit by the rotation of thepipe string.

Thus, at the present time, the majority of drilling operations areconducted by employing rotary drilling equipment. In conventionalrotary. drilling, a hollow jointed steel shaft called the drill stem isrotated from the surface of the earth. This shaft, extending downwardlyinto the earth to'any desired depth, rotate a drill bit. For a number ofreasons, there are attached, to the lower end of the drill pipe, heavysections of pipe termed drill collars. Also, for a number of purposes, aweighted liquid called drilling mud is circulated in one directionthrough the drill stem and in the opposite direction through the annulusbetween the drill stem and the borehole. In these drilling operations,it is known that rocks subjected to alternating stresses will failrapidly in .fatigue. This effect is responsible to some extentfor theaction of conventional rock bits, wherein toothed cutters rolling on thesurface of the rock impart alternating stresses to the surface of therock, resulting in chipping, fracturing, and crumbling of the 'rockbeing drilled. The conventional rock bit, however, depends to a verygreat extent for its cutting action upon compressive stress induced byextreme weight on the bit. This is secured by allowing the weight of'thedrill string to partially rest on the bit. This process, while entirelysatisfactory, has a number of inherent difficulties. may be incompression, resulting in buckling of the pipe which in instances causesthe hole to deviate from the vertical. vFurthermore, the stressinduceddue. to the buckling and unbuckling of the compressed pipe results'incorrosion fatigue. To reduce this difficultyjdrill collars, which areheavy lengths of pipe, are used. These are expensive and are subject tofrequent failures. Another disadvantage is that the friction against thewalls of the hole causes the drill pipe to wind up, with the resultvthata substantial amount of bouncing of the bit occurs on the bottom ofthehole. This aggravates the wearing of the cutter bearings in rock bits.Thus, this is not 'anfefiicient way to induce alternate stresses of themagnitude and For example, part of the drill pipe Thus, the principlesof this invention may be appreciated by considering simple drillingtests. Thus, in shattering hard formations with a drill as, for example,of the nature of the star drill, it can be readily established that themost effective penetrating force is achieved by imparting a combinationtorsional and percussive action to the drill bit. The resultant motionat the actual drill teeth or other cutting surfaces is downwardlyinclined and results in an inclined force which serves to hammer andshear the formation encountered by the drill. Depending upon thecomposition of the formation to be drilled, thelongitudinal andtorisonal components of the drill movement should be varied for bestresults. Again, depending on the composition of the formation to bedrilled, the phase relationship between the downward and rotary motionof the drill should be varied. In this connection, it is a principalobject of this invention to provide a simple and effective drillingapparatus capable of varying the phase .and magnitude of the combinedlongitudinal and torsional vibrations that are applied to a drill bit.It is also an object of the invention to separately or jointly controlthe amplitudes of the vibrations.

In addition to the observation that a combination torsional andpercussive action in a drill. bit provides the most effectivepenetrating force, it has also been observed that other factors havepronounced effects upon the effec tiveness and efficiency of a drillingapparatus or method. Furthermore, it has been found that these factorstend to differ markedly in their relative importance, depending upon thetype of formation being drilled, the depth of the formation, etc.

Accordingly, it is one object of the present invention to provide adrilling apparatus which is superior to existing apparatus and methodsin its ability to drill effectively and efliciently through a widevariety of earth formations. It is another object of the invention toprovide a drilling apparatus which is much more readily adapted to changing drilling conditions than are conventional apparatus and methods. Itis stillanother object of the invention to. greatly reduce the time andmoney that are presently required in drilling a borehole by greatlyreducing the time required to ascertain and adjust to the best drillingconditions for various formations and structures that are penetrated bythe borehole.

, Q While, as pointed out above, a vibratory bit such as de-' scribed inUS. 2,554,005, issued May 22, 1951, Earth.

Boring Apparatus, A. G. Bodine, In, possesses many advantages, the enerydissipation to thesurrounding liquid In accordance with the presentinvention, this energy dissipation is materially decreased by utilizinga unique gaseous buffer zone positioned'in the bit assembly. A specificadaptation is to employ an annulus which is filled with an inert gas,such as air or nitrogen. A

particular apparatus is one that, when thepressure builds up in thedrill pipe, a differential area valve opensthe pressure chamber to anorifice so as to very slowly bleed nitrogen or other inert gas into thepocket and maintain a gas buiier pocket while drilling. By this method,the pressure from the escaping gas also forces mud and shaleaccumulation from the pocket.

The apparatus of the present invention may be more fully understood byreference to the attached drawings illustrating embodiments of the same.

FIGURE 1 illustrates the gas pocket wherein the pocket is open to thesurrounding liquid drilling fluid.

FIGURE 2 illustrates an adaptation of the present invention wherein thegas surge pocket is separated from the surrounding drilling liquid bymeans of a movable piston element.

Referring specifically to FIGURE 1, a drill bit assembly is showndisposed in the bottom of borehole l which extends to the earthssurface. The drill bit assembly is attached to the lower end of drillcollar 2. For the purposes of clarity and simplicity, the deviceimparting the vibratory motion to the drill bit assembly which ispositioned generally at the upper end of the drill collar is not shown,since these means are well known in the art. The vibration-inducingapparatus may be hydro-driven or may be of the electrical type such as amagnetostnictive transducer or solenoid driven. Also for the purpose ofsimplicity, the mechanical filter or isolator positioned be tween thedrill stem and the drill collar is not shown, since these devices arealso well known in the art. In general, these filters or isolationdevices prevent the vibratory motion from being imparted upwardlythrough the drill stem.

These filters may be of the air-pocket type or springactuated type.

As pointed out heretofore, the present invention is particularlyconcerned with a drilling apparatus wherein high firequencies areemployedas, for example, frequencies in the range from about to 500cycles per second. A particularly desirable frequency is about 300cycles per second. In general, the amplitudes vary from about 0.0001 to0.25 inch. A desirable amplitude is in the range of about 0.01 inch.

The drill bit assembly, as illustrated in FIGURE 1, which is attached tothe lower end of drill collar 2 comprises an upper cylindrical butlerelement 3 which contains a hollow annulus 4 positioned between an innerwall 20 and an outer wall 6.

A satisfactory type bit 7 is attached tothe lower end of cylindricalbutter element 3. This bit may be of any type employed in rotarydrilling, such as a fish tail bit, a star bit, or the frusto-conioalroller-type bit.

Cylindrical element 3 containing a hollow annulus is characterized byhaving said annulus sealed into upper and lower separated spaces. Thelower space of said annulus, comprising a surge chamber 8, communicatesat its lower end to the annulus between the borehole Wall and wall 6through ports 9.

In operation, the upper space or chamber of said annulus is filled atthe surface with gas through filler valve 10 so as to secure arelatively high-pressure gas in the upper space of said annulus. Ametering valve 11 is adjusted so as to permit a predetermined rate offlow through said valves when a bleeder valve 12 is opened ashereinafter described.

The assembly is lowered into the well borehole after the upper space ofsaid annulus is filled to high pressure with inert gas. The mud pumpsare then started, forcing mud, liquid, or other suitable drilling fluiddownwardly within the pipe stringthrough mud channel 13 within saidcylindrical element, through bit 7, and upwardly in the annulus betweenthe pipe string and the borehole wall. This mud pressure will exert athrust on bleeder valve 12. Thus, inert gasas, for example,nitrogen-will flow through metering valve 11, through bleeder valve 12,into the upper portion of surge chamber 8. 7

Thus, as the drill bit assembly vibrates as hereinbefore described, gasaccumulated in surge chamber 8will compress and decompress to compensatevolumetrically forliquid movement caused by the motion of the vibratingsteel. The gas being compressible, little energy is consumed in thevibrating process. By operating in this manner, the major part of theenergy otherwise lost in lifting a long column of drilling liquid(generally known as pumping the liquid) is eliminated or materiallyreduced.

Referring specifically to FIGURE 2, the apparatus is substantiallysimilar to that described with respect to FIGURE 1. Similar parts ofFIGURE 2 are numbered identically with the corresponding par-ts ofFIGURE 1. FIGURE 2 shows a doughnut-shaped piston element 15 positionedabove ports 9 which in eflect substantially seals ott the upper end ofsurge chamber 8 from contact with the drilling liquid. In operation, thepiston moves upwardly and downwardly, thus acting as a cushion for thevibratory movements and thereby materially decreasing the energy whichwould otherwise be lost to the surrounding liquid. Piston 15 is providedwith a check valve 16 which permits the gas to bleed from the surgechamber to the liquid when the pressure within the surge chamber exceedsa predetermined maximum.

As pointed out heretofore, the invention is concerned with an improvedapparatus for drilling when utilizing vibratory drilling techniques. Bythe utilization of a gaseous surge chamber, appreciable amounts ofenergy are conserved which can greatly increase the effectiveness andrapidity of the drilling rate.

Having described the invention, it is claimed:

1. An improved vibratory bit assembly which comprises a bit attached tothe lower end of an elongated cylindrical absorber, the upper end. ofsaid absorber being attached to the lower end of a drill collar, saidabsorber being characterized by having an inner wall which forms a continuous and uninterrupted passageway from within said drill collar towithin said bit, said absorber having an outer wall thereby forming anannular space between said inner and said outer walls, a partitionWithin said annular space to form a top annular chamber. and a bottomannular chamber separated one from the other, ports in the outer wall atthe lower end of said bottom annular chamber thereby forming apassageway from within said bottom annular chamber to the exterior ofsaid absorber such that the volume of said annular chamber is insubstantially direct fluid communication with the exterior of theabsorber, and valve means controlled by mud pressure for permittingcontinuous controlled flow of gas from said top annular chamber to theupper section of said bottom annular chamber.

2. Apparatus as defined by claim 1 including a doughnut-shaped movablepiston in said lower annular chamber at a point above said ports.

3. An apparatus of the character described and of a character to beinserted between a drill bit and the lower end of drill string whichcomprises in combination: a body member of a character to be attached atits upper end to the lower end of said drillstring and attachable at itslower end to said bit, said body member having a pas sage therethroughestablishing fluid communication between the interior of said drillstring and the interior of said bit; a chamber in said body member andof a character to retain therein 'gas under high pressure; a surgechamber in said body member having a port in the lower portion thereofestablishing substantially direct fluid communication between thesubstantially complete interior of said surge chamber. and theexteriorof said body member; a passageway between said chamber and said surgecharm ber; and valve control means in said passageway, said valve meansbeing of a character'to openwhen the pressure within said passagereaches a predetermined value to engaging the walls of said chamberabove said port.

' 5. In a'drilling system using a circulating drilling fluid 6 andwherein a vibratory vertical thrust is imparted to a 6. An apparatus asdefined in claim 5 wherein said rotating bit rotated by a drill string,an apparatus for surge pocket contains an inert gas. minimizing energydissipated to the drilling liquid which 7. An apparatus as defined inclaim 6 wherein said comprises: means for establishing a gaseous surgepocket inert gas comprises nitrogen. at the lower end of the drillstring; means for continuously 5 injecting gas into said surge pocketduring the circulation References Cited in the file of this patent ofdrilling fluid; means for maintaining direct fluid communication betweenthe gas in said surge pocket and drill- UNITED STATES PATENTS ing fluidin the space adjacent said bit whereby gas 210- 2,554,005 Bodine May 22,1951 cumulated in the surge pocket compresses and deco-m- 10 2,815,928Bodine Dec. 10, 1957 presses to compensate volumetrically for liquidmovement 2,824,718 Currie Feb. 25, 1958 caused by the motion ofvibrating vertical thrust.

